The present invention relates to an image forming apparatus such as a plane paper color copy machine and a printer, for printing data transferred from an image data supplying apparatus such as a personal computer and a digital camera, on plane papers or OHP sheets. Particularly, this invention relates to a fixing device having a cooling mechanism for cooling a medium to be taken out when a paper jam occurs while fixing a color material deposited on the medium.
An image forming apparatus is generally equipped with an optical unit, an exposure unit, a developing unit, a paper-feeding unit, a transfer unit, a fixing unit, and so on.
The paper-feeding, transfer and fixing units would suffer a paper jam in which any of the units is jammed by sheets of paper as an image forming medium on which an image is formed.
A paper jam could occur anywhere in the units to which sheets are transferred. When a paper jam occurs in the fixing unit that has been generating a high heat, a user has to open a hinged door of an image forming apparatus to find a unit that has been suffering a paper jam for taking out the jamming sheets (a jam process).
Such a jam process annoys a user, particularly when it occurs to the fixing unit because jamming papers are often heated when a hinged door of an image forming apparatus is opened due to the facts that a paper jam occurs right after a fixing process or a heat-generating fixing unit is very close to the papers.
Rapid cooling to the fixing unit for taking out the jamming papers when a paper jam occurs around the fixing unit could cause temperature decrease to the fixing unit while toner has been attached to the unit, the cooled toner being hardly peeled off.
A purpose of the present invention is to provide an image forming apparatus having a cooling mechanism that offers a jam process without annoying a user when performed to a fixing unit, and without getting a fixing roller dirty by cooling only the outlet of the fixing unit and its peripheral.
In order to meet the purpose, a fixing device of an image forming apparatus according to the first basic configuration of the present invention is an fixing device of an image forming apparatus, heated and fixed by which is an image forming medium transferred on which is a toner image formed on an image fixing body by an electrophotography process, the fixing device including: a fixing unit that presses and heats the image forming medium to be fixed by a pair of fixing rollers; medium holding means provided at an outlet side of the fixing unit for holding the image forming medium, on which an image has been fixed, transferred and discharged from the fixing unit; jam detecting means for detecting a jam in which the image forming medium has been caught between the fixing rollers and not moving; cooling means including a cooling mechanism for cooling the medium holding means and jamming image forming medium and a drive mechanism for driving the cooling mechanism; and drive admitting means for admitting the drive mechanism to drive the cooling mechanism to cool the medium holding means and the jamming image forming medium located in the vicinity of the medium holding means when the jamming image forming medium is detected by the jam detecting means.
The drive admitting means may include a manual switch that is provided inside a door provided at a front body of the image forming apparatus, for the cooling means to start by a user manual operation. Or, it may be an automatic drive admitting means by which a switch is turned on when the door provided at the front body is opened. Moreover, it is preferable that, under combination of the manual switch and automatic control, for example, the cooling means is automatically driven when the door is opened to cool at once the medium holding means and a jamming image forming medium that is located in the vicinity of the medium holding means, and the cooling means is stopped by means of the manual switch when the medium holding means and the jamming image forming medium have been cooled enough.
For drive admission by a manual operation, it is preferable that the drive mechanism of the cooling means is stopped when a user has not depressed the manual button anymore.
For automatic control, it is preferable that, after the driving mechanism of the cooling means has started to drive, cooling is performed for a fixed period in which the drive mechanism has continued driving until a predetermined period passes, and the drive mechanism automatically stops when the predetermined period has passed.
The cooling means may, in general, be constituted by a cooling fan as a cooling mechanism and a motor as a drive mechanism for rotating the cooling fan. The drive admitting means as a manual operating means thus can be an on-off switch for a cooling fan-driving motor. The cooling means may be constituted, as a unique configuration, by a cooling mechanism in which a refrigerant pipe is provided along the bottom of a receiving plate of the medium holding means, such as, a discharge transfer guide and a drive mechanism for cooling by circulating a refrigerant through the refrigerant pipe of the cooling mechanism.
Configured as above, when a paper jam occurs in the fixing unit, a discharge transfer guide at the discharge side and an image forming medium, such as, a jamming sheet that has been discharged to the discharge side only are cooled without cooling the fixing unit itself. Therefore, a user can take out an image forming medium caught in the fixing unit with no uncomfortable feeling when performing a jam process.
Moreover, the medium holding means, such as, a guide at the discharge side and an image forming medium, such as, a jamming sheet located in the vicinity of the medium holding means only are cooled without sending a cool wind or cool air to the fixing unit itself, thus no occurrence of attachment of toner, for example, to the fixing rollers due to cooling. The present invention thus achieves a cooling mechanism of a fixing device easy for post-processing.
A method of controlling a cooling mechanism of a fixing device according to the second basic configuration of the present invention is a method of controlling a cooling mechanism of a fixing device of an image forming apparatus, heated and fixed by which is an image forming medium transferred on which is a toner image formed on an image fixing body by an electrophotography process, the fixing device including a fixing unit that presses and heats the image forming medium to be fixed by a pair of fixing rollers, medium holding means provided at an outlet side of the fixing unit for holding the image forming medium, on which an image has been fixed, transferred and discharged by the fixing unit, jam detecting means for detecting a jam in which the image forming medium has been caught between the fixing rollers and not moving, and cooling means including a cooling mechanism for cooling the medium holding means and jamming image forming medium and a drive mechanism for driving the cooling mechanism, the method including the steps of: detecting a jam in which the image forming medium has been caught between the fixing rollers and not moving by the jam detecting means; and admitting the drive mechanism to drive the cooling mechanism to cool the medium holding means and the jamming image forming medium located in the vicinity of the medium holding means.
In the method of controlling a cooling mechanism of a fixing device according to the second basic configuration, the step of admitting the drive mechanism to drive may include the step of driving the drive mechanism of the cooling means by a user manual operation.
In this method, the step of driving by the user manual operation may be performed by depressing a drive switch for starting the drive mechanism to drive the cooling mechanism.
In this case, it is preferable that the cooling means includes a cooling fan as the cooling mechanism for sending a specific airflow in a direction of the medium holding means and a drive motor as the drive mechanism for rotating the cooling fan, the step of driving by the user manual operation being performed by depressing a drive switch for starting the drive mechanism to drive the cooling fan provided in the vicinity of the fixing rollers.
Moreover, in this case, it is preferable that the cooling means includes a refrigerant cooling unit as the cooling mechanism that is provided at a transfer plate that is included in the medium holding means, for cooling the transfer plate by using a refrigerant and a refrigerant circulating unit for circulating the refrigerant of the refrigerant cooling unit, the step of driving by the user manual operation being performed by depressing a drive switch for driving circulation of the refrigerant of the refrigerant cooling unit provided at an outlet side of the fixing rollers.
In the method of controlling a cooling mechanism of a fixing device according to the second basic configuration, the step of admitting the drive mechanism to drive may include the steps of: generating a control signal based on the jam detected by the jam detecting means; and automatic admission step of automatically driving the cooling means based on the control signal.
In this method, the automatic admission step may include the steps of: detecting that a door provided at a front body of the image forming apparatus has been opened, thus outputting a drive admitting signal; and driving the drive mechanism of the cooling means based on the output drive admitting signal.
In this case, it is preferable that the cooling means includes a cooling fan as the cooling mechanism for sending a specific airflow in a direction of the medium holding means and a drive motor as the drive mechanism for rotating the cooling fan, the automatic admission step including the steps of: detecting that the door at the front body has been opened, and outputting the drive admitting signal to the drive motor; and driving the drive motor by means of the output drive admitting signal.
Furthermore, in this case, it is preferable that the cooling means includes a refrigerant cooling unit as the cooling mechanism that is provided at a transfer plate that is included in the medium holding means, for cooling the transfer plate by using a refrigerant and a refrigerant circulating unit for circulating the refrigerant of the refrigerant cooling unit, the automatic admission step including the steps of: detecting that the door at the front body has been opened, and outputting the drive admitting signal to the drive mechanism; and driving the drive mechanism by means of the output drive admitting signal.
Moreover, in this method, the automatic admission step may include the steps of: detecting that a door provided at a front body of the image forming apparatus has been opened, thus outputting a drive admitting signal; driving the drive mechanism of the cooling means based on the output drive admitting signal; and a manually operating step of manually operating a drive shut-down switch to stop the cooling mechanism.
Accordingly, the method of controlling a cooling mechanism of a fixing device according to the second basic configuration of the present invention can basically effectively drive the cooling mechanism of the fixing device according to the first basic configuration. The method thus achieves effective cooling to the medium holding means at the outlet side of the fixing unit and the image forming medium transferred and discharged onto the medium holding means, without cooling the fixing device itself, and also without making a user uncomfortable and attachment of toner to the main mechanism of the image forming apparatus.